On this day: March 12

2011: A reactor at the Fukushima Daiichi Nuclear Power Plant melts down, exploding and releasing radioactivity into the atmosphere a day after Japan was struck by a powerful earthquake and tsunami. In the hours and days that followed, two more reactors at the plant experienced full meltdown. It was the largest nuclear disaster since the Chernobyl disaster of 1986, and only the second disaster to measure Level 7 on the International Nuclear Event Scale.